I think this is likely a very good idea. I've thought about the idea of channels a lot building https://wingman.actor and I've gone back in forth on if channel primitives are a good idea at a low level or if existing chat clients are just an already well defined utility you shouldn't rewrite.

I think your approach of a unified SDK/data structure around a chat that adapts to different clients is a really strong solution that probably just gives you the best of both worlds.